MLX73290RLQ-BBM-000-TU

MLX73290-M and MLX73290-A Application Note - RF Self Polling Scope This document provides a detailed description of the RF self-polling mode that can be configured in the Melexis RF transceiver ICs MLX73290-M and MLX73290-A (both called MLX73290 in this document). Self-polling is realized by an integrated timer with very low power consumption. The polling mode wakes up the RF receiver or transmitter after a programmable time and scans one or more frequency channels for valid data. It can also be used to transmit the same data periodically. 1) RF Receiver Self Polling The MLX73290 can be configured in automatic polling mode, using a programmable interval based on a 16bit timer clocked with the internal calibrated RC oscillator (typ. at 15.6kHz), pre-scaled by a binary power of 215 giving a maximum interval of 38 hours. Polling mode must be activated by the two registers POLL_RFRX and EN_POLL (POLL_RFRX enables the RF RX polling and EN_POLL enables the RF polling timer). a) Polling periods Polling grid Offset Period Period Period Rx state MLX73290 in polling mode It is possible to define an offset to decide when to start polling. The offset and polling period are configured with the registers POLL_EXP[3:0], POLL_OFFSET[15:0] and POLL_PERIOD[15:0] according to the following formulas: 𝑂𝑓𝑓𝑠𝑒𝑡 = 2(11+𝑃𝑂𝐿𝐿𝐸𝑋𝑃) . (1 + 𝑃𝑂𝐿𝐿𝑂𝐹𝐹𝑆𝐸𝑇 ) [𝑠𝑒𝑐] 𝑓𝑋𝑇𝐴𝐿 𝑃𝑒𝑟𝑖𝑜𝑑 = 2(11+𝑃𝑂𝐿𝐿𝐸𝑋𝑃) . (1 + 𝑃𝑂𝐿𝐿𝑃𝐸𝑅𝐼𝑂𝐷 ) [𝑠𝑒𝑐] 𝑓𝑋𝑇𝐴𝐿 At the end of the waiting period, the timer restarts and sets the corresponding IRQ flag TMR_FLAG, the MLX73290 is set in receiver mode looking for a valid synchronization word (SYNC_WORD[31:0]), during a certain time. 3901173290 Rev 003 1/5 AN73290 Self Polling Jan/2016 MLX73290-M and MLX73290-A Application Note - RF Self Polling b) Termination timer The termination timer is programmable between 64 μs and 34 s (RXTERM_MANT[3:0] and RXTERM_EXP[3:0]).  When RXTERM_EXP = 0 𝑡𝑒𝑟𝑚𝑖𝑛𝑎𝑡𝑖𝑜𝑛 𝑡𝑖𝑚𝑒𝑟 =  211 . (1 + 𝑅𝑋𝑇𝐸𝑅𝑀𝑀𝐴𝑁 ) 𝑓𝑋𝑇𝐴𝐿 When RXTERM_EXP is between 1 and 15 𝑡𝑒𝑟𝑚𝑖𝑛𝑎𝑡𝑖𝑜𝑛 𝑡𝑖𝑚𝑒𝑟 = 211 . (𝑅𝑋𝑇𝐸𝑅𝑀𝑀𝐴𝑁 + 17). 2(𝑅𝑋𝑇𝐸𝑅𝑀𝐸𝑋𝑃−1) 𝑓𝑋𝑇𝐴𝐿 Polling grid Offset Rx state MLX 73290 in polling mode Period Period Period Termination timer When the timer expires, termination may be postponed while RSSI is above the threshold, or while payload is being received, depending on the setting of the bit RXTERM_COND. Then the state machine will take the action selected by RXTERM_ACT: it will stop or recalibrate and resume reception.  After timeout has expired, postpone termination if RXTERM_COND is equal to: o 0 = always (i.e. never terminate) o 1 = never (i.e. terminate unconditionally) o 2 = as long as RSSI is above threshold, or payload is being received (after detection of a valid sync word) o 3 = as long as a payload is being received Furthermore, there is the option to set a threshold RX_RSSI_TH on the RSSI.  Action to take for RX termination timeout is selected by RXTERM_ACT: o 0 = go to error state o 1 = flush RF RX FIFO, recalibrate RX, then RX 3901173290 Rev 003 2/5 AN73290 Self Polling Jan/2016 MLX73290-M and MLX73290-A Application Note - RF Self Polling The example below with RXTERM_COND = 3 and RXTERM_ACT = 0 shows when a packet received is longer than the termination timer: Polling grid Period Period Offset Termination timer* Rx state MLX73290 in polling mode RF signal received by the MLX73290 *The termination timer is postponed as long as a payload is being received. c) Recalibration The RX period might be preceded by periodic recalibration as configured by CALIB_MODE[0:2].  Periodic (re)calibration mode: o 0 = always recalibrate o 1 = 1:4 o 2 = 1:8 o 3 = 1:16 o 4 = 1:32 o 5 = 1:64 o 6 = 1:128 o 7 = never recalibrate Example below with CALIB_MODE = 1: Polling grid Offset Period Rx state MLX73290 In polling mode Period Period Period Period Termination timer Recalibration 3901173290 Rev 003 3/5 AN73290 Self Polling Jan/2016 MLX73290-M and MLX73290-A Application Note - RF Self Polling d) Example The RF state machine will eventually return to its stopped (idle) state after completion of the task (e.g. packet received) or when an error occurs (e.g. RX termination timer expires, PLL out of lock, FIFO overrun etc.). In the meantime, the polling timer continues to run, so the polling grid is in no way affected by how long it takes the RF transceiver to return to its idle state. This is important for RF protocols with beacons or timeslots at fixed intervals. The following picture shows the basic functionality of the RF polling feature when a packet is longer than the polling period. Polling grid Offset Period Period Period Recalibration Rx state MLX73290 in polling mode Termination timer* RF signal received by the MLX73290 RF still busy not restarted *The termination timer is postponed as long as a payload is being received. Settings:    CALIB_MODE = 0 RXTERM_COND = 3 RXTERM_ACT = 0 2) Continuous Current Consumption in Receive Mode Parameter Sleep mode current RF Receive mode current Symbol 𝐼𝑆𝐿𝐸𝐸𝑃 𝐼𝑅𝑋,315𝑀𝐻𝑧 𝐼𝑅𝑋,433𝑀𝐻𝑧 𝐼𝑅𝑋,868𝑀𝐻𝑧 𝐼𝑅𝑋,915𝑀𝐻𝑧 Test conditions RCO timer on 100kbps, FSK, NRZ Typical 0.6 14 15 16 17 Units µA mA 3) Timer Settings Period Termination timer Sleep timer Offset timer 3901173290 Rev 003 Min Max 33.55 sec 64 µs 38.17 hours 4/5 Step 64 µs AN73290 Self Polling Jan/2016 MLX73290-M and MLX73290-A Application Note - RF Self Polling 4) Polling Grid Examples To reach an average current consumption of for example 2mA, the polling grid could have the following structure: Termination period in s 1 2 4 8 16 33.55 Sleep period in s 8.3 15.7 29 60 116 230 With the longest termination period of 33.55 seconds, the average current consumption can be decreased further using the following sleep period: Average current in mA 15 10 5 2 1 0.5 0.2 0.1 0.05 0.02 0.01 0.006 Sleep period in s 2.2 20 75 230 (3.8 min) 500 (8.3 min) 1,000 (16.6 min) 2,700 (45 min) 5,400 (90 min) 11,000 (3 h) 29,000 (8 h) 61,000 (17 h) 112,000 (31 h) The average current consumption as a function of sleep period and termination period can be illustrated as follows: Receiver polling - timing examples 4.5 4.0 3.5 3.0 average RX current 2.5 (mA) 2.0 1.5 1.0 0.5 1 3 5 7 9 11 13 15 17 19 0.0 termination period (ms) sleep period (s) 3901173290 Rev 003 5/5 AN73290 Self Polling Jan/2016 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Melexis: MLX73290KLQ-BBM-000-RE MLX73290KLQ-BBM-000-SP MLX73290KLQ-BBM-000-TU MLX73290RLQ-BBM-000TU MLX73290RLQ-BBM-000-SP MLX73290RLQ-BBM-000-RE MLX73290RLQ-ABA-000-RE MLX73290RLQ-ABA000-SP